F 12
A table is given the annual values of the magnetic elements in 1930 as derived from 52 determinations:
Declination (West) 0.43.6 Dip (North) 30.37.3 Horizontal Force (C. G. S. Unit) 0.37485 Vertical Force (C. G. S. Unit) 0.22187 Total Force (C. G. S. Unit) 0.43559Photographic registration of magnetic declination, horizontal force and vertical force was maintained throughout the year, except during periods of adjustment. The correct interpretation of the records is doubtful, however, owing to the difficulty of determining the temperature co-efficients of the force variometers accurately, and the instability of the declination base-line. A new mirror for the latter is on order from England, and it is hoped that abnormalities will disappear after its installation.
The records show that the temperature co-efficients of the horizontal and vertical force variometers are considerable, and pending the installation of an efficient temperature regulator, experiments with a control magnet for the horizontal force variometer are in progress.
The following table gives temperature data for the magnetograph room during the year 1930.
Month Temperature Daily Range Mean Absolute Maximum Absolute Minimum Absolute Maximum Absolute Minimum Mean January 67.6 54.7 2.9 0.7 1.3 February 74.5 54.8 2.6 0.4 1.6 March 75.6 60.9 4.3 0.1 1.5 April 83.2 72.1 2.5 0.7 1.4 May 87.6 82.0 2.5 0.8 1.4 June 91.5 81.7 2.6 1.0 1.7 July 91.6 84.0 2.3 0.8 1.4 August 92.5 84.3 2.3 1.0 1.5 September 92.0 81.1 1.8 0.5 1.2 October 85.4 79.9 2.3 0.9 1.6 November 84.3 74.3 3.3 1.0 1.6 December 76.6 64.7 3.7 0.0 1.5